The present invention relates to cast members having gaskets embedded therein and more particularly a novel method and apparatus for producing cast members having cast-in gaskets of a boot design which are uniquely adapted for use in cast members having openings of reduced size.
Cast members, such as, for example, manhole assemblies, have been traditionally used in sewage systems and networks and the like and are comprised of manhole assemblies having openings each adapted to receive a pipe in order to provide for inflow and outflow of liquid. It is conventional to provide gaskets within the aforesaid openings which cooperate with the pipe pushed therethrough to form a watertight seal, both the advantages and necessities for a watertight seal being well known in such sewage systems and the like.
With the constant desire to reduce the cost of both the manufacturing and materials employed in the production of cast members being ever present, one of the traditional approaches has been to produce gaskets of reduced size and hence reduced rubber (or rubberlike) content. One such gasket is described in U.S. Pat. No. 5,529,312, which patent teaches a gasket having a boot portion which is folded over to lie against a main gasket portion preparatory to casting. The gasket is placed upon a mandrel secured to one of the walls forming the mold assembly. The wall is moved to the closed position whereupon the cast material typically concrete) is poured into the mold. The mold assembly is opened after the cast material has cured. The boot portion is then unfolded preparatory to use. A pipe is pushed through the gasket including the boot portion. A steel clamp is placed around the boot portion to provide a watertight seal.
In order to reduce the amount of rubber utilized in the gasket disclosed in the aforementioned ""312 patent, the overall size of its opening may be reduced; however, in order to provide a capability of controlling opening size, permissible angular deflection and permissible redial deflection, the only parameter of the ""312 gasket which may be regulated is gasket thickness.
It is therefore extremely desirable to provide a gasket which is capable of controlling opening size, and angular and radial deflection through variation of a gasket parameter other than gasket thickness.
The present invention is characterized by comprising method and apparatus for providing manhole assemblies and the like having a gasket embedded therein and which is designed to provide simplicity of manufacture, assembly and use.
The gasket, in one preferred embodiment of the present invention, comprises an annular-shaped base portion having integral anchoring means extending radially outward therefrom. The base portion is shaped to form a substantially U-shaped radius portion having an annular-shaped boot portion integrally joined to the radius portion and extending in a generally axial direction. The free end of the boot portion is provided with an annular head portion defining a clamp receiving portion. The gasket is made of a suitable rub or rubber-like material of a suitable durometer such as 40 to 45 durometer. In order to produce a cast member having the aforesaid gasket anchored therein, a mandrel assembly is provided, which assembly is comprised of an inner mandrel in the form of a substantially flat, disc-shaped member having a threaded member axially aligned with the center thereof and extending in a direction perpendicular to the mandrel surface. The inner mandrel may have a shape to fit the back area to the radius.
The outer mandrel, having a substantially truncated, hollow, conical configuration, cooperates with the inner mandrel to retain the gasket in the proper position within the mold assembly. The boot portion of the gasket is passed through the smaller diameter end of the outer mandrel until the radius portion engages the annular edge thereof. The inner mandrel is placed against the radius portion of the gasket on the convex side thereof. A star-shaped retaining member is placed upon the threaded member. The portion of the boot which would otherwise extend outwardly from the outer mandrel is bent in an inward radial direction, and is held down by the retaining member so as to be confined within the interior of the outer retaining ring in order to avoid any interference with the casting operation. The xe2x80x9cpushed-inwardxe2x80x9d portion of the boot and the retaining member are held in place by a suitable threaded nut which threadedly engages the threaded member. The combined mandrel assembly and gasket is placed within a casting mold by conventional means.
The cast material is then poured into the mold. Once the cast material has been cured, the mold is opened, the mandrel assembly is disassembled and removed, enabling the inwardly curved boot portion to resume its normal, substantially annular-shaped configuration.
A pipe is pushed through the gasket to a depth sufficient to assure that the pipe extends beyond the free end of the boot, enabling the boot to be firmly secured to the pipe extending therethrough by means of stainless steel take-down clamp which is tightened to an extent sufficient to assure a water tight seal which meets and, in fact, surpasses ASTM specifications.
The above-described embodiment is extremely advantageous for use in flat wall structures as well as curved wall structures when the piping seal allows for the connector to be installed in a flat plane.
In applications where it is not possible to install a take-down clamp in a flat plane, as in the first embodiment, the present invention provides an alternative embodiment in which the boot portion is provided with a plurality of convolutions which enable the water stop portion of the gasket to be cast on a severe curve while the stainless steel clamp is capable of being fixed in a flat plane by serving as a resilient xe2x80x9cbufferxe2x80x9d region between the clamp and the radius portion. The installation of the second embodiment is substantially the same of that of the first.
Both of the described embodiments comprise radius portions which can be increased or decreased to provide for greater or lesser annular space between the inside opening of the entry hole and the outside diameter of the pipe. The radius further provides the desired tolerance for angular deflection of the pipe, as well as, off-set placement in both the vertical and horizontal positions which parameter is capable of being adjusted, in addition to and independently of gasket thickness.